Abstract
CBL interacting protein kinases play important roles in adaptation to stress conditions. In the present study, we isolated a CBL-interacting protein kinase homolog (AdCIPK5) from a wild peanut (Arachis diogoi) with similarity to AtCIPK5 of Arabidopsis. Expression analyses in leaves of the wild peanut showed AdCIPK5 induction by exogenous signaling molecules including salicylic acid, abscisic acid and ethylene or abiotic stress factors like salt, PEG and sorbitol. The recombinant AdCIPK5-GFP protein was found to be localized to the nucleus, plasma membrane and cytoplasm. We overexpressed AdCIPK5 in tobacco plants and checked their level of tolerance to biotic and abiotic stresses. While wild type and transgenic plants displayed no significant differences to the treatment with the phytopathogen, Phytophthora parasitica pv nicotianae, the expression of AdCIPK5 increased salt and osmotic tolerance in transgenic plants. Analysis of different physiological parameters revealed that the transgenic plants maintained higher chlorophyll content and catalase activity with lower levels of H2O2 and MDA content during the abiotic stress conditions. AdCIPK5 overexpression also contributed to the maintenance of a higher the K+/Na+ ratio under salt stress. The enhanced tolerance of transgenic plants was associated with elevated expression of stress-related marker genes; NtERD10C, NtERD10D, NtNCED1, NtSus1, NtCAT and NtSOS1. Taken together, these results indicate that AdCIPK5 is a positive regulator of salt and osmotic stress tolerance.
Highlights
Plants have developed an elaborate network of signaling pathways to counter the challenges posed by various stressful environmental conditions
Arabidopsis AtCIPK24/ SOS2 was initially identified as an AtCBL4 target protein that participated in salt tolerance mechanism by activating the Na+/H+ antiporter located on the root plasma membrane[11,12], while AtCBL10-AtCIPK24 system was shown to be involved in the maintenance of Na+ homeostasis in shoots and leaves[13]
A full-length cDNA of AdCIPK5 gene that was identified in differential gene expression analysis was cloned using the sequence of a partial cDNA from a wild peanut, Arachis diogoi[21] using Rapid amplification of cDNA ends (RACE)-PCR approach
Summary
Plants have developed an elaborate network of signaling pathways to counter the challenges posed by various stressful environmental conditions. Several CBL proteins have been identified from different plants[7] These proteins act as sensor relays and target a family of Ser/Thr kinases known as CBL-interacting protein kinases (CIPKs). Arabidopsis AtCIPK24/ SOS2 was initially identified as an AtCBL4 target protein that participated in salt tolerance mechanism by activating the Na+/H+ antiporter located on the root plasma membrane[11,12], while AtCBL10-AtCIPK24 system was shown to be involved in the maintenance of Na+ homeostasis in shoots and leaves[13]. Studies have shown that its wild relatives exhibit the high level of tolerance to various biotic and abiotic stress conditions[20] and Arachis diogoi is one of them. Tobacco transgenic plants overexpressing AdCIPK5 were checked for tolerance against various stress treatments These observations are reported in this communication
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